I recently came across a Pony Express marker way off the Pony Express Trail. It sits in Rio Vista, California, and commemorates the New World, the river steamer that may have carried the first eastbound rider from San Francisco to Sacramento. The other contender for this distinction is the Antelope. There is a monument to that steamer in Old Town Sacramento.
Rio Vista sits in the Delta, a huge wetland area in the middle of the Central Valley with over a thousand miles of levies. It’s where the Sacramento River (from the north) meets the San Joaquin River (from the south). Once merged, both turn west to flow into San Francisco Bay. This estuary was the main avenue of travel up into the gold mines, which lie east of the Delta.
The town is forty or so miles south of Sacramento, and so far as I know there is no regular ferry service between Sacramento and San Francisco. If you ride the Pony Express Bikepacking Route to Sacramento—even if you continue all the way to San Francisco—you won’t see this town or this monument unless you make a special trip. There is a lot of nice riding between Sacramento and Rio Vista, and some very cool old towns. There are even a couple of state-run ferries to take you across sloughs (the rides last all of about three minutes). But it is quite a way off the Pony Express land route.